Focus on whitefly – how to treat and prevent them in your garden

Thanks for all your questions over the past week – I love hearing from you and answering your questions. If it is a question I get asked a lot, it usually inspires my next blog post, sharing my practical experience. All the knowledge I share with you has come from being in the soil and growing organic food for the past 30 years – it is my passion.

I have been out every day harvesting my tomatoes and removing the disease – for me it will soon be time in the cycle to pull these plants out. The humidity is a perfect breeding ground for disease, and in my neck of the woods, we have had plenty of this! My basil and chillis are loving it and growing in size daily, no matter how much I harvest.

This week, I want to focus on the pesky whitefly, how to treat an infestation and – even better – how to prevent them.

So what are whitefly?

Whiteflies are tiny, white, sap-sucking insects that are only 1-2mm long. The nymphs (babies) and the adults both suck the sap of a plant. This makes the plant weak, and whitefly can also spread disease which arrives when the plant lacks the immunity to fight it off.

When the weather is warm and humid the pesky whitefly breed like rabbits! The female lays her eggs, anywhere from about 250 – 500 eggs on the underside of the leaf. They are cunning little creatures, so it always pays to look under the leaves on your plants regularly, as you won’t see the damage until it has taken hold and weakened your plants.

The eggs hatch into crawling, sap-sucking nymphs anywhere between 4 and 12 days. They crawl away from the eggs and flatten themselves onto the underside of the leaves and stay there until they become adults. They go from egg to adult in approximately 25 days.

When whitefly feed on the sap of your plant, they excrete honeydew which, if left on the plant, can cause sooty mould to grow on the leaves, which in turn can prevent photosynthesis and create poor health.

If you’re not familiar, photosynthesis is the process used by plants to gather energy from sunlight, water and carbon dioxide (gases that are in the air) and out of this, they make glucose which is what every plant needs to survive.

So how do I treat whitefly organically?

Whitefly that live in a greenhouses are different from those that live on outside plants, which is important to be aware of when you’re treating it.

I use Enspray 99, Kelp and EM all together as a combined secret weapon to protect against whitefly. Enspray 99 is a bio gro certified organic product I sell, which is effective by sticking to the leaves when sprayed. It then suffocates the whitefly and also acts as a deterrent for more egg laying. I add Kelp and EM (Effective microorganisms) to it for optimum plant health.

When spraying, tap the plant first and spray in the air as whitefly will naturally fly upwards. Give the plant a good soaking on the underside of the leaves. Within a week, if you rub the underside of the leaf, the whitefly will come off. Usually, I will repeat this process on a monthly basis, but if it is really bad, I will spray every two weeks. Remember to always rinse your sprayer out and pump some clean fresh water through the hose and nozzle to prevent build up.

In a greenhouse, hang up yellow sticky traps – you can even make them at home with yellow card smothered in Vaseline and a hole punched in them and hung up.

How can I prevent these pests?

A good diverse range of beneficial insect plants will help, as these will bring in lacewings that feed on the whitefly – harnessing nature to take care of your problems.

Sacrificial plants are a great organic method to prevent whitefly – essentially these plants will become the host plant of the infestation, and could eventually die, as this is its purpose.

Calendula officinalis, Nasturtium and Nicotiani are all great sacrificial plants. When you have these in the garden and observe the flowers, you will see early warning signs of whitefly as they love these plants.

Plants that whiteflies particularly like are citrus, brassicas (cabbage, cauliflower and kale) and in the greenhouse, they seem to love a lot of plants!

In the summer months, I don’t eat my kale as I use it for a host plant for the whiteflies. This means they will all gather there and lay their eggs rather than on my other summer plants. Nature working in harmony!